Origin

An old Scandinavian word which goes back even further to the same source as Latin sedere ‘to sit’. The Latin word is also the origin of sedentary (late 16th century), sedative (Late Middle English), and sediment (mid 16th century), and from its past tense session (Late Middle English) literally an act of sitting, so settling down to deal with something. The sense ‘a place where a government is based’, as in seat of government or power, comes from the throne or ‘seat’ of a king or governor. American pilots in the 1940s were the first to use by the seat of the pants, meaning that they flew the plane using their instinct and experience rather than relying on the aircraft's instrument panel. An experienced pilot could tell by a change in the vibrations of the seat if, for example, the plane was about to stall, and so take early action to rescue the situation.